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Frank- somehow a helicopter crashing in Garrett County (presumably from the weather) didn't make the Sun! Here is a link from the Cumberland Times-News.
http://www.times-news.com/policelog/local_story_007231425.html?keyword=topstory

NAO is an effect...not a cause. The NAO state is a measure of atmospheric pressure differences over two stations in the north Atlantic. It/s an observation.

What caused the cold outbreak was a stratospheric warming event during late NOV / early DEC. This caused the polar vortex to slow...split in two...and reverse direction...creating an anti-cyclonic (clock-wise)circulation aloft. The reversal took about 3 weeks to propagate to the surface...creating HIGH pressure over the pole....which in turn created favorable conditions for arctic outbreaks...such as the one currently observed.

These reversal events occur preferentially during years (such as this one) where an east wind is observed in the tropical stratosphere (quasi-biennial oscillation - QBO) and solar activity (sunspots) is low. Above normal snowfall in eastern Eurasia this fall played a significant role in initiating the stratospheric warming event.

HIGH pressure @high-latitudes are indicated by negative NAO and the Arctic Oscillation (AO). To blame the cold on -NAO is just plain wrong.

According to Professor Mojib Latif from Germany, eminent climate scientist and leading member of the UN's Intergovernmental Panel on Climate Change, this "short" cold period isn't as short as you might think. It's the beginning of a 20-30 year cooling cycle just as the warming cycle we're now leaving wasn't due to human-caused global warming, but rather to the normal cycles the planet goes through.

FR: You (and the Daily Mail and George Will) are twisting his position. Here's an interview with NPR in which he tries to clarify misinterpretations of his work by GW deniers. He makes it clear he believes GW is and will remain a real issue after any short-term cooling has passed: "However, if we look further, then we have some indications that there are after, say after 2015 or 2020, you know, global warming will accelerate again." Here's the interview: http://bit.ly/5GEpde

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Frank Roylance is a reporter for The Baltimore Sun. He came to Baltimore from New Bedford, Mass. in 1980 to join the old Evening Sun. He moved to the morning Sun when the papers merged in 1992, and has spent most of his time since covering science, including astronomy and the weather. One of The Baltimore Sun's first online Web logs, the Weather Blog debuted in October 2004. In June 2006 Frank also began writing comments on local weather and stargazing for The Baltimore Sun's print Weather Page. Frank also answers readers’ weather queries for the newspaper and the blog. Frank Roylance retired in October 2011. Maryland Weather is now being updated by members of The Baltimore Sun staff